1. Field of the Invention
The present invention relates to an exposure apparatus for exposing a substrate to radiant energy, an information processing apparatus for determining a shot layout used by the exposure apparatus, and a method of manufacturing a device using the exposure apparatus.
2. Description of the Related Art
Along with the recent demand for finer, higher-density circuit patterns, a projection exposure apparatus for manufacturing a semiconductor device is required to project a circuit pattern formed on an original (which can also be called a mask or reticle) onto a substrate (e.g., a wafer) with a higher resolving power. The apparatus is also required to improve a process performance (throughput) which can be represented by the number of substrates that can be processed per unit time, in order to obtain high productivity. Because accuracy and throughput are contradictory performance items for a general semiconductor manufacturing apparatus, a large number of measurements to increase accuracy can decrease throughput. To improve throughput while maintaining accuracy, the following techniques are available.
As the first technique, a minimum number of most effective shots (to be referred to as sample shots hereinafter) serving as samples used in measurement are designated for each type of measurement. In particular, the selection of a different shot layout for each type of measurement and as well as effective sample shots based on the given layout in one recipe decreases the number of measurements of each type to be performed.
As the second technique, the angle of view of one exposure (shot) is set relatively large. Decreasing the number of shots per substrate greatly improves the throughput of the exposure apparatus. For example, when four chip regions can be exposed by one shot, the throughput improves as compared with a case in which only one chip region is exposed by one shot.
As the third technique, two stages are used. Nowadays, two substrate stages are often built in one exposure apparatus. The two substrate stages are generally used to parallelly perform a measurement process and exposure process. When the time spent for the substrate exposure process is sufficiently longer than that for the substrate measurement process, more various types of measurement necessary for the substrate can be performed, thus allowing high-accuracy alignment and the like. Still better, the throughput becomes less likely to decrease with a large number of types of measurement.
Consider a recipe as an instruction issued to the exposure apparatus to expose a substrate. Of recipe constituent elements, shot layout designation is especially important from the viewpoint of ensuring both accuracy and the throughput. As described above, a shot layout which assigns an importance to the throughput is generally designed to increase the area of each shot region as much as possible so that the number of times of exposure per substrate decreases. However, the tilt of a substrate often differs between its central portion and peripheral portion. When all shot regions are processed using the same angle of view, the tilt cannot be followed, which may result in an unusable chip. In that case, the process engineer can, for example, edit a shot layout and continue a subsequent lot process. If the process engineer empirically knows this fact in advance, he/she may generate a shot layout by dividing a shot region that is likely to be defective into shot regions as small as the chip size in advance at the stage of creating a recipe.
However, even when a shot layout is edited, it is not always suitable because each substrate has a different surface shape. Conversely, when a shot region that has no defect in surface shape is divided, the throughput often decreases.